1 20 Processes for preparing Lake from Madder. 



tirely lost the peculiar odour of the root, and only retain a 

 faint woody smell. 



The water loaded with the colouring matter must be 

 put into an earthen or well tinned copper, or, what is still 

 better, a silver vessel, (lor the use of iron must be carefully 

 avoided throu2;h the whole,) and heated till it just boils. 

 It must then be poured into a laro;e earthen or porcelain 

 bason, and an ounce troy weight of alum dissolved in about 

 a pint of boiling soft water must be poured into it, and 

 stirred until it is thoroughly mixed. About an ounce and 

 a half of a saturated solution of mild vegetable alkali should 

 be gently poured in, stirring the whole well all the time. 

 A considerable effervescence will take place, and an immer- 

 diate precipitation of the colour. The whole should be 

 suffered to stand till cold ; and the clear yellow liquor niay 

 then be poured oft' from the red precipitate. A quart of 

 boiling soft water should again be poured on it, and well 

 stirred. When cool, the colour may be separated from the 

 liquor by tjltratioa through paper in the usual way ; and 

 boiling water should be poured on it in the filter till it 

 passes through of a light straw colour, and quite free from 

 any alkaline taste. The colour may now be gently dried j 

 and when quite drv it will be Jound to weigh half an ounce ; 

 just a fourth part of the weight of ihe madder employed. 



By analysis, this colour possesses rather more than AO 

 percent, of alumine. If less than an ounce of alum be 

 employed with t\^■o ounces of madder, the colour will be 

 rather deeper; but if less than three quarters of an ounce 

 be used, the whole of the colouring matter v.-ili not be com- 

 bined with alumine. On the whole, I consider the pro- 

 portion of an ounce of alum to two ounces of madder, as 

 the best. 



Process 2. 



If, when the solution of alum is added to the water 

 loaded with the colouring matter of the root, the whole be 

 suffered to stand, without tlie addition of the alkali, a con- 

 siderable precipitation will take place, which will be of a 

 dark dull red. The remaining liquor, if again heated, will, 

 by the addition of the alkali, produce a rose-coloured pre- 

 cipitate of a beautiful tint, but wanting in force and depth 

 of tone. 



This is the process recommended by Mr. Watt, in his 

 Essay on Madder, in the A)ivaLes dn Chymh', tome 7 ; and 

 this kcter coiour is what may, perhaps with propriety, be 

 called madder lake. But, although the lighter red may be 



excellent 



